Method of manufacturing continuous electrodes



Jam E7 195@ R. TANBERG $495348 METHOD OF MANUFACTURING CONTINUOUS ELECTRODES Filed July 17, 1946 Maven-mm. fiHCFNHR ma ma ATTORNEY.

Patented Jan. 17, 1950 METHOD OF MANUFA CTURING CONTINUOUS ELECTRODES Ragnar Tanberg, Drammen, Norway Application July 17, 1946, Serial No. 684,096

In Norway May 8, 1943 Section 1, Public Law 690, August 8, 1948 Patent expires May 8, 1963 3 Claims. 1

The known type of continuously self-burning electrodes is based on melting down in a sheet iron pipe a plastic mass consisting of crushed anthracite or coke, to which are added pitch and tar as binding agent. As this mass becomes completely liquefied by heating and firstly assumes a solid state and then is coked at relatively high temperatures, it is necessary that the sheet iron pipe follows the electrode mass down into the bath and is here corroded away with the same. it is here to be noted that coking of the mass is necessary in order to obtain a sufliclent electrical conductivity.

Still another reason why the sheet iron pipe may not be separated from the mass is that the latter sticks and adheres to the sheet iron. The disadvantage of this electrode is that the sheet iron envelope increases the cost of the electrode, nrlinarily because of the relatively high costs of manufacturing the envelope, which generally takes place by welding or riveting. Further the addition of iron received by the bath through melting down of the sheet pipe may act uniavorably in certain metallurgical processes.

A constructional form oi self-burning elec trodes has been suggested in which the sheet iron pipe or mantel is avoided by suspending the electrode at its lower portion, which has heen burnt to such a degree that it has sufiicient to permit of the attachment of the suspension means.

The diiliculty of constructing a continuous electrode without an iron mantel has been that has had no binding agent for the mass which,

a relatively moderate temperature imparts mechanical firmness to the same or permits of coking without mass adhering to the mantel. one is to operate with an electrode without iron envelope, it is necessary to place the merit supplying jaws a distance below the zone which the electrode mass is suificien'tly coked order to be current carrying. in case this does not take place before at a very high temperature near the bath surface it will not be possible in practice to maintain a lasting current The present invention has for its object to avoid the disadvantages mentioned above in the completely continuous electrodes now used.

if the binding agent is of such a nature that it binds and cokes at a relatively moderate temperature, at 200-300 C., for example it is possible in practice in this zone, without difllculty, to supply the current by means of ordinary current supplying laws.

iii

Nor is it dimcult at this 66 2 temperature to undertake the necessary control of the rate of feeding of the electrode.

According to the invention it has been found that in evaporated sulphite waste lye from the cellulose industry or other aqueous solutions of saccharldes, tanning acids, resins and substances which carbonize exothermally, for example lignin and derivatives of lignin of substantially the same composition as sulphite waste lye, one has a means which in an astonishing way fulfills the requirements of a binding agent for obtaining satisfactory results. Such materials give a binding agent which binds the electrode mass without the latter adhering to the surrounding iron mantel, because the mass shrinks and is solidified when subjected to light drying and because the coking begins at moderate, low temperatures and thereupon continues exothermally.

In practice one may easily produce such a solution with properties as mentioned above by evaporation of sulphite lye to a dry material content of about 50%. it has been found that in the use of an electrode mass based on the employment of sulphite lye as binding agent in so small quantities that the mass does not adhere substantially to the shaping iron cylinder, such a, great binding power is obtained through a subsequent light drying at low temperatures that the electrode mass may be slid out of the shag ing pipe and he sufficientiy mechanically strong to constitute an indenendei'lt electrode body which may he passed down into the melting bath without support from the shaping cylinder.

it has further been found that during the said drying of the mass the latter is completely released from the iron cylinder so that the ready dried and shaped electrode haimay be easily moved out of the shaping pipe.

it has been found that the quantity of suiphite lye which should be added in order to obtain a suflicient binding power may advantageously be fixed at between ill-35%, and that the subsequent drying may suitably take place at a temperature of above loll C.-"lld C.

By the expression sulphite waste lye as used above and in the claims shall be understood waste lye from the production of sulphlte cellulose, regardless of Whether it refers to the ordinary sulphite process, which operates with calcium bisulphite, or other sulphite processes, for example one in which ammonia bisulphite is used.

A solution according to the invention may eventually also be produced by the mixing of its individual components. By way of example may 3 be mentioned a solution produced by mixing and heating to 80-90" C. oi

Per cent Glucose 5-10 Tannin 12-21 Natural resins Calcium salt of lignosul phonic acid (finely divided or decomposed lignin) 17-28 Water 40-60 The mass which is mixed and stamped down into the shaping pipe and dried as mentioned above, has the qualit that it cokes relatively easily at moderate temperatures because a temperature of about 250 C. will initiate a coking process which develops exothermally, whereby coking is easilyobtained.

Because in the melting processes for which this type of electrodes is employed ample heat quantitles of the temperatures here discussed are available, it follows that in practice one may expedite the coking of the electrode mass so that it becomes sufilciently electrically conductive for the connection of electric current supplying jaws at a point of the electrode bar at which the temperatures are still so moderate that this may be done without practical difliculties.

As will be understood, the invention will be particularly applicable in connection with a stationary pipe or mantel, mounted above the bath, which shapes the electrode and holds it together until the mass, through the influence of heat, has turned consistent so that it may be passed down into the furnace as it is being consumed.

According to'an embodiment of the invention there is mounted around the shaping pipe or mantel, a casing of heat resisting material, through which the hot gases from the melting bath are passed in such a way that the pipe and consequently the electrode mass is heated to a few hundred degrees, so that the mass which is passed through the pipe stiffens and hardens and forms a firm, glutinated mass. In the appended drawing this embodiment is shown diagrammatically: I designates the furnace arch, 2 the bath surface and 3 the casing of heat resisting material mounted on the furnace arch. In the upper closed end of this casing is placed the shaping pipe 4, which at the top is provided with a funnel shaped expansion 5 in which the electrode mass consisting of a premixed mass of, for example 90% cokeand/or anthracite powder and about concentrated sulphite lye is stamped down. The hot gases from the furnace pass through the casing 3 and out through a discharge pipe 1, which is provided with a control damper 8. Through influence of heat from the gas the electrode mass will first stiffen and thereupon coke to a consistent electrode. Below the pipe 4 are mounted current supplying jaws, in-

dicated by 9. The current is supplied through the lead III, which is suitably passed through the casing I.

I claim:

1. In the process of forming continuous electrodes from a mixture of a crushed carbonaceous material and a binding agent for electric furnace use, the improvement which consists of employing evaporated waste sulphite lye as the binding agent, said evaporated waste sulphite lye having a dry material content of 50-60% and constituting from 10% to of the total electrode mass.

2. In the process of forming continuous electrodes from a mixture of a crushed carbonaceous material and a binding agent for electric furnace use and wherein the mixture is glutinated and coked in a heated guiding mantel, the improvement which consists of employing evaporated waste sulphite lye as the binding agent, said evaporated waste sulphite lye having a dry material content of 50-60% and constituting from 10% to 35% of the total electrode mass.

3. The process of claim 2 further characterized in that the mixture of the electrode forming materials is heated to a temperature of froml50 to 300 C. while in said mantel.

RAGNAR TANBERG.

file of this patent:

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